The present invention is directed to the addition of a triglyceride in a deinking process.
Paper is a renewable resource and can be recycled to make new paper. Papers that can be recycled include, but are not limited to, newspaper, mixed office waste, and magazine paper. In order to be recycled, the paper is repulped into cellulose fibers. The fibers are swelled with alkaline water to form an aqueous slurry to assist in detaching the ink particles from the fibers. In order to remove these detached ink particles from the slurry, many deinking processes are available.
One method of deinking is washing. In wash deinking, at least one surfactant is added to make the ink hydrophilic, and to allow the ink to be washed away. The particle size of the ink is generally about 2-20 xcexcm in order to allow the ink particles to flow through a fiber mat.
Another deinking method is froth flotation. A gas, such as air, is passed through the slurry, and the ink particles attach themselves to the air bubbles in the slurry. These bubbles rise to the top of the slurry and form a froth layer at the surface, which is then removed. It is desired to remove as much ink as possible in order to reduce the dirt counts and increase brightness of the paper. It is desired to keep the ink hydrophobic in this process. Also, the ink typically has a particle size of 10-200 xcexcm. The upper limit of the particle size is limited by the ability to keep the ink particle attached to the air bubble. If the particle is too large, then the ink particles will detach from the bubble.
Generally, deinking agents are added to assist in detaching and the subsequent removal of the ink from the cellulose fibers. Generally, deinking agents include one or more surfactants. Surfactants are surface active agents that alter the surface properties of the ink particles. In wash deinking, surfactants form micelles for holding the ink particles. Ink particles are generally hydrophobic, and the surfactant makes the ink particle more hydrophilic and allows the ink to remain in the aqueous phase without being redeposited onto the paper fibers. In flotation deinking, on the other hand, added surfactants cause ink particles to be more hydrophobic. Also included in the repulping and deinking process are bases, such as alkali metal hydroxides; alkali metal silicates; chelating agent, and bleaching agents.
Fatty acid soaps have been used in deinking of old newsprint as an ink collector for subsequent removal via froth flotation in many deinking systems. This chemical, while useful, often requires the end user to convert fatty acid to fatty acid soaps on site resulting in significant capital costs.
The application of the fatty acid soap also requires the use of a metal source, such as calcium. In the case of calcium, the source can be calcium chloride or lime, which is added to provide the free metal ions needed to form the insoluble soap. Problems associated with the addition of calcium are corrosion due to the excess chlorine and/or scale formation of calcium carbonate. Additionally, the use of fatty acid soaps can generate excessive foam in the deinking process.
It would be desirable to reduce either the amount or eliminate the use of fatty acid soaps. This could result in a savings of capital, operating costs, and could reduce or eliminate corrosion or scaling.
The present invention provides a method of deinking paper comprising providing a paper slurry, wherein at least a portion of the paper contains a marking material, and treating the paper slurry with a deinking composition comprising at least one triglyceride.